In my recent columns I've been critical of calls for a global "blasphemy" ban from the Organization of Islamic Conference and other Muslim leaders. But free-speech protections, if they are to be meaningful, must be universal. The greatest threat to them is double standards that are the bedrock of advocacy for the slippery slope of restrictions.

Some Muslims and their sympathizers point to anti-"hate speech" laws in Canada and some European countries as an example of double standards or how restricting the content of speech can be compatible with liberal values.

Precisely because these objections are plausible in the general Western, if not American, contexts, they again demonstrate how pernicious such bans are. The best defense has been that the United States, with its extremely permissive atmosphere on expression, provides a better aspirational model.

But even in the United States there are lurking threats to free speech designed to stifle political expression. One of the most troubling recent examples of this is an effort by members of the California State Assembly to urge or coerce public universities in California to crack down on "anti-Semitic hate speech" in the name of defending Jewish students and other supporters of Israel.

A recently passed non-binding resolution by the assembly includes a disturbingly over-broad definition of "anti-Semitism." It includes numerous kinds of overtly political opinions, including calls to boycott, divest from or sanction Israel; suggestions that Israel is a racist, apartheid or Nazi-like state; or that Israel has engaged in crimes against humanity such as ethnic cleansing or genocide. Even more absurdly, it defines anti-Semitism as holding Israel to standards of behavior not required of "any other democratic nation," or questioning the legitimacy or propriety of maintaining Israel as a Jewish state.

This dangerously over-broad definition of anti-Semitism is based on working documents published in 2005 by the European Monitoring Centre on Racism and Xenophobia. Its orientation reflects a mistake common to anti-hate speech efforts. Rather than attempting to establish any kind of clear, coherent guideline for distinguishing between anti-Semitic speech and what is simply unpleasant or provocative speech, it functions as a catchall. It prefers to include anything that might conceivably be a vehicle for anti-Semitism, even when that's probably not the case. There are analogous definitions of Islamophobia that are equally pernicious.

Even though much of what is described above, and in the resolution, isn't necessarily, or even probably, genuinely anti-Semitic, this still begs the question of what the California legislature is doing pressuring public universities on the subject of speech. The controversy over the resolution, and its unworkable definition of anti-Semitism, demonstrates that the state, including public universities, has no business trying to regulate speech unless absolutely unavoidable. It reveals that, especially on questions involving Israel, what is labeled anti-Semitic is often highly subjective, and, worse still, highly politicized.

The California legislature was responding to recommendations by a campus committee on anti-Semitism that recommended a ban on "hate speech." Phobic, abusive, fear or hate mongering, and highly offensive speech is a real problem in free societies. Measures to respond to it by restricting speech, however, are a perfect example of the purported cure that is worse than the perceived disease.

When the crackpot historian David Irving was given a prison sentence in Austria for lectures in which he questioned the historicity of the Holocaust, almost all mainstream Jewish-American groups condemned or distanced themselves from laws criminalizing such stupid and offensive opinions. Yet some of these same organizations have been strongly supportive of the California campus "hate speech" crackdown campaign.

Fortunately, it won't work. Experience suggests that "hate speech" bans invariably fail and frequently boomerang on the groups initially pushing for them. Certainly in the United States, the default towards free speech is strong enough that a position advocating censorship is almost always a losing one, socially, politically and legally.

In Western societies that try to restrict "hate speech," the enforcement of such laws is almost always a political struggle that illustrates the inherent subjectivity at play. The cases invariably highlight the tension between the value of free expression and misguided efforts to get the state to forcibly protect society from unpleasant, provocative, bigoted or racist opinions.

Muslim advocates of a global "blasphemy" ban are right that efforts to restrict "hate speech" undermine Western claims about free expression and raise the issue of double standards. But the answer isn't to extend such restrictions even further to cover "blasphemy." It is to recommit to the value of free speech.

No good can come from trying to use state power to suppress offensive expression. Those who politicize such efforts do the most harm, because their double standards are evident and motivations obvious. Muslims who would restrict speech to "protect Islam" have no greater allies than Jews who would do so to "protect Israel."